Fix AS7726 not showing serial number in 'show platform summary' (#10489)

[FuzailBrcm]

Why I did it

AS7726 platform was not showing serial number in the output of

• show platform summary
• show version
  Issue [ACCTON/PDDF] Show platform summary display serial number=N/A on as7726 #10489

How I did it

Th root cause was that thePDDF chassis common class was reading the 'service_tag' upon invoking get_serial(). However, Accton platform AS7726 did not have service tag programmed in the EEPROM. Hence throwing 'N/A'

How to verify it

• show platform summary
• show platform version

root@sonic:/sys/bus/i2c/devices# show ver

SONiC Software Version: SONiC.master.0-dirty-20220408.025810
Distribution: Debian 11.3
Kernel: 5.10.0-8-2-amd64
Build commit: 50067c8e4
Build date: Fri Apr  8 10:03:36 UTC 2022
Built by: fk410167@sonic-lvn-csg-004

Platform: x86_64-accton_as7726_32x-r0
HwSKU: Accton-AS7726-32X
ASIC: broadcom
ASIC Count: 1
Serial Number: 772632X1911067
Model Number: FP3ZZ7632074A
Hardware Revision: N/A
Uptime: 10:54:30 up 17 min,  1 user,  load average: 0.87, 0.91, 0.82
Date: Fri 08 Apr 2022 10:54:30

Docker images:
REPOSITORY                    TAG                              IMAGE ID       SIZE
docker-platform-monitor       latest                           6d11a86a79be   519MB
docker-platform-monitor       master.0-dirty-20220408.025810   6d11a86a79be   519MB
docker-dhcp-relay             latest                           6134df8859e5   427MB
docker-sonic-telemetry        latest                           02f2bdff3ca6   506MB
docker-sonic-telemetry        master.0-dirty-20220408.025810   02f2bdff3ca6   506MB
docker-router-advertiser      latest                           4186dc554e53   417MB
docker-router-advertiser      master.0-dirty-20220408.025810   4186dc554e53   417MB
docker-database               latest                           f3ff7e7a38f5   417MB
docker-database               master.0-dirty-20220408.025810   f3ff7e7a38f5   417MB
docker-orchagent              latest                           38289831c04a   437MB
docker-orchagent              master.0-dirty-20220408.025810   38289831c04a   437MB
docker-fpm-frr                latest                           6c146abbc4f3   438MB
docker-fpm-frr                master.0-dirty-20220408.025810   6c146abbc4f3   438MB
docker-nat                    latest                           3a07c488cbc5   423MB
docker-nat                    master.0-dirty-20220408.025810   3a07c488cbc5   423MB
docker-sflow                  latest                           58c97022daf1   421MB
docker-sflow                  master.0-dirty-20220408.025810   58c97022daf1   421MB
docker-teamd                  latest                           77b13fe63153   420MB
docker-teamd                  master.0-dirty-20220408.025810   77b13fe63153   420MB
docker-macsec                 latest                           d3f757f29037   423MB
docker-macsec                 master.0-dirty-20220408.025810   d3f757f29037   423MB
docker-snmp                   latest                           87255f532f0b   449MB
docker-snmp                   master.0-dirty-20220408.025810   87255f532f0b   449MB
docker-syncd-brcm             latest                           0c1f4caa79f1   784MB
docker-syncd-brcm             master.0-dirty-20220408.025810   0c1f4caa79f1   784MB
docker-gbsyncd-credo          latest                           d2585339145a   422MB
docker-gbsyncd-credo          master.0-dirty-20220408.025810   d2585339145a   422MB
docker-lldp                   latest                           d4a5b441d5e6   445MB
docker-lldp                   master.0-dirty-20220408.025810   d4a5b441d5e6   445MB
docker-sonic-mgmt-framework   latest                           dc235a4f16fd   549MB
docker-sonic-mgmt-framework   master.0-dirty-20220408.025810   dc235a4f16fd   549MB
docker-mux                    latest                           dbcc3675685e   458MB
docker-mux                    master.0-dirty-20220408.025810   dbcc3675685e   458MB

root@sonic:/sys/bus/i2c/devices# show platform summary
Platform: x86_64-accton_as7726_32x-r0
HwSKU: Accton-AS7726-32X
ASIC: broadcom
ASIC Count: 1
Serial Number: 772632X1911067
Model Number: FP3ZZ7632074A
Hardware Revision: N/A
root@sonic:/sys/bus/i2c/devices#

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)